Antenna pane including coating having strip-like segmented surface portion

ABSTRACT

An antenna pane for use, for example, as a vehicle window, comprises a glass pane ( 1 ) carrying an electrically conductive coating ( 3 ). The coating ( 3 ) includes a strip-like portion ( 5 ) divided into electrically isolated segments by barrier lines ( 4 ) spaced so the coating transmits HF radiation in a specified frequency range and constructed, by contacting in contact areas ( 7 ) at its two longitudinal sides ( 6 ) and by its outer dimensions, as a slot antenna for frequencies in said range.

The invention concerns an antenna pane comprising at least one glasspane and at least one electrically conductive coating which issubdivided by barrier lines into a number of electrically isolatedsegments on which antenna pane the coating incorporates at least onestrip-like segmented surface portion in which the distance between thebarrier lines is so small that the coating there can transmit HFradiation in a specified frequency range.

Glass panes which are provided with electrically conductive coatings,particularly with solar control coatings, and on which the coatingnormally covers the greater part of the glass pane, have already beenput to use in various ways as antenna panes, mainly, but notexclusively, as motor vehicle glass. Accordingly, it has been suggestedthat the conductive coating itself be used as a monopole-type antenna(e.g. DE 37 21 934 A1). It has also been suggested that the coating besubdivided into electrically isolated segments to optimise the antennafunction (e.g. DE 36 41 738 A1, JP A 62-193 304). The opportunities fordesigning the antenna in this way are limited.

Antenna panes on which a strip-like, non-coated area in an electricallyconductive coating or surrounding this can be used as a slot antenna arealso known, e.g. from EP 0 332 898 B1 and EP 0 760 537 B1. An antennapane with a number of slot antennas is described in DE 101 46 439 C1held by the applicant.

It has been suggested as an alternative to direct utilisation of theelectrically conductive coating for antenna purposes that the coating beprovided full-surface or partly with a raster of non-conductive barrierlines to enable it to transmit HF radiation and thereby separateantennas arranged behind the coating, viewed from the transmitter'spoint of view, to be used (e.g. EP 0 531 734 A1, DE 195 08 042 A1, EP 0717 459 A1). The barrier lines are generated preferably by means of alaser and are so close together that they can transmit HF radiation withpolarisation perpendicular to the run of the lines in a specifiedfrequency range.

An antenna pane of this type on which the invention is based is found,for example, in WO 96/31918 A1. The strip-like segmented (rastered)surface portions suggested there, in which the distances between thebarrier lines are so small that the coating there can transmit HFradiation, have the purpose of enabling separate antennas on whichbecause of the segmentation the reception is not appreciably impaired bythe electrically conductive coating to be arranged in theHF-transmitting areas thus formed. A disadvantage of this solution isthat additional transmission lines are indispensable for the antennafunction and accordingly the manufacture of the antenna panes becomesmore complex and production costs are increased. This also runs contraryto the efforts made by the motor vehicle industry to keep the number ofwire-type or printed conductors in the vision area of the panes as lowas possible for the sake of the clearest possible view and of safety.

The invention is based on the problem of specifying an antenna pane withan electrically conductive coating which requires no additional printedor wire-type transmission lines and which can be rationally produced.The inventive measures are intended to impair the view through the paneas little as possible, offer the antenna expert great freedom of antennadesign and enable the integration of antennas for different frequencyranges. At the same time it should be possible to easily integrateheating elements or other electrical functions into the antenna pane.

It is suggested in accordance with the invention that the segmentedsurface portion is by contacting in the contact areas at its twolongitudinal sides and by its outer dimensions constructed as a slotantenna for electromagnetic radiation in the range of frequencies whichthe segmented surface portion can transmit.

This means by which a surface portion of the coating is made directlyable to transmit HF radiation and so usable as an antenna, that is, as aslot antenna, by segmentation enables the coated pane to be providedsurprisingly easily with a diversely optimisable antenna function. Asuitable frequency range for which the slot antenna is designed, takinginto consideration the usual dimensions of motor vehicle panes in themeter range, is particularly, but not exclusively, the VHF range (30-300MHz).

The segmented surface portion is normally arranged completely inside thecoating and thus enclosed by this on all sides. In this case for theslot antenna formed in accordance with the invention to function it isnot absolutely necessary for the antenna pane to be surrounded by metalbodywork in the installed condition. It is however within the scope ofthe invention to provide for the segmented surface portion to be locateddirectly at the edge of the pane so that the metal bodywork at leastalong one (longer) side of the segmented surface portion acts as a metalsurround for the slot antenna formed by this and is incorporated intothe antenna function.

As regards the preferred width of the barrier lines and the maximumbarrier line distance required for HF-transmissibility reference is madeto the aforementioned publications (EP 0 531 734 A1, DE 195 08 042 A1,EP 0 717 459A1). HF-transmissibility as envisaged by the invention isachieved if the transmissibility for the specified frequency range is atleast about 50%. Expressed in another way, this means that theattenuation caused to incident HF radiation by the coating in thesegmented surface portion is not more than about 3 dB in the specifiedfrequency range.

It goes without saying that particularly when barrier lines are providedfor in the vision area of the antenna pane, their width should be keptas narrow as possible. The lower limit of the line width here isdetermined by the need to prevent short circuiting between adjacentsegments as far as possible to prevent impairment of the antennafunction and undesirable current flows. A barrier line width of about0.05-0.1 mm has proved effective in practice. To achieve sufficientHF-transmissibility, the distances between barrier lines in thedirection of polarisation should be considerably less than a fifth andpreferably considerably less than a tenth of the relevant wavelength.

In an initial, particularly simple embodiment of the invention from theproduction point of view it is provided for that the barrier lineswithin the segmented surface portion form a linear or lattice rasterwith a constant raster unit size.

A further optimisation of the antenna function, on the one hand, and areduction of the processing time for generating the barrier lines, onthe other, enables another preferred variant in which the barrier lineswithin the segmented surface portion form a raster with a variableraster unit size, variable barrier line width or variable raster form.It has been found that the raster unit size formed by the barrier linesin the end areas of the segmented surface portion used as a slot antennamay, if necessary, be larger than in its central area, in whichcontacting normally takes place. Here it is taken into account that thefield amplitude inside a slot antenna is at its greatest in the middle(antinode) and at its lowest at the ends (oscillation nodes). Thisenables the overall length of the barrier lines, by contrast with avariant with constant raster unit size, to be reduced without having tosuffer a loss of antenna power. It is also possible to vary the barrierline width or above all the raster form and so achieve antennaoptimisation or reduction of the production time. Accordingly thesegmented surface portion used as a slot antenna will normally besegmented in the form of a lattice raster; here in particularrectangular and above all square rasters have proved effective forachieving HF-transmissibility for all directions of polarisation.However, depending on the contour of the strip-like segmented surfaceportion and the direction of polarisation of the HF-radiation to bereceived by the slot antenna, it can suffice to generate merely a linearraster in some areas.

It is within the scope of the invention instead of straight barrierlines to use undulating, curved, zigzagged, fractal or othernon-rectilinear barrier lines. This enables, for example, a higher slotantenna bandwidth or special optical effects to be achieved.

An antenna pane optimised for multi-range reception is distinguished inthat the segmented surface portion is designed as a slot antenna for theVHF range, that in a part of the segmented surface portion a rasterwhich can transmit frequencies above the VHF range and is finer than inother areas of the segmented surface portion is provided for and that inthis part at least one antenna is arranged for frequencies above the VHFrange. The antenna for higher frequencies can be arranged as a separateantenna, if necessary, in another plane of the pane. Preferably,however, it is also generated directly from the coating with the aid ofbarrier lines.

This is achieved particularly easily if the segmented surface portionincorporates a constriction reducing the width of the segmented surfaceportion in the area in which it is contacted as a slot antenna. In thecase of this embodiment it is not only the contacting of the slotantenna which is facilitated. If the constriction also comprises a stripof the electrically conductive coating projecting into the segmentedsurface portion, which is designed as a monopole or dipole antenna forone frequency range or more than one frequency band above the receptionrange of the slot antenna, additional transmission lines can bedispensed with for this frequency range. As regards the form of themonopole or dipole isolated from the coating, for example, arrangementsknown principally from DE 101 46 439 C1 or other forms familiar to theexpert can be used.

It goes without saying that the antenna pane, as well ashigher-frequency antennas which are preferably integrated into thesegmented surface portion, can also incorporate lower-frequencyantennas, particularly for the AM band. These can, as is known, bearranged as separate antennas in an HF-transmitting area or before orbehind this. It is however also possible, and preferable within thescope of the invention, to isolate a sufficiently large area of thecoating from the rest of the coating by barrier lines and wire it as anAM antenna; here care must be taken to isolate electrically from the AMantenna areas of the coating close to the bodywork in the installedcondition in order to prevent coupling of the AM antenna to the bodyworkand so reducing the antenna output.

The antenna pane can easily be functionally extended to form a heatableantenna pane, if the coating comprises a heatable area provided with busbars and electrically isolated by at least one barrier line from thearea of the pane adjacent to the segmented surface portion. Here it canbe provided for that the heatable area is provided with barrier lineswhich influence the distribution of the heating current. Such anarrangement is especially advantageous from the production point ofview, since—except for the antenna contacts or bus bars required for theheating and antenna function—no additional conductors are required toprovide the heating function. Rather it is sufficient merely toincorporate some further barrier lines into the coating in addition tothe barrier lines provided for the antenna function in accordance withthe invention. With the aid of these further barrier lines, on the onehand, a heatable area is generated from the coating and electricallyisolated from the area used for antenna purposes with its segmentedsurface portion and, on the other, the heatable area can, if desired ornecessary, be provided in a known way (e.g. U.S. Pat. No. 4,459,470 A1,DE 15 40 764 A1, DE 36 44 297 A1) with barrier lines so as to enablelocal overheating to be prevented or a particular local distribution ofthe heating effect to be achieved.

If in addition to the slot antenna according to the invention furtherantennas are to be integrated into the heatable antenna pane, it canparticularly be provided for that the heatable area is used in a knownway as an antenna for the VHF and/or AM range. It is also possible withthe aid of barrier lines to generate directly in the coating additionalantenna structures for high-frequency antennas, such as GPS antennas orantennas for electronic key systems (keyless entry), passive switchingelements such as capacitances or inductances, feed conductors and thelike.

Even if the invention aims as far as possible to avoid additionalantennas or heating conductors, it is nevertheless within its scope toprovide for such additional conductors as required, if, for example, theheating effect of the electrically conductive coating is insufficient orthe antenna function is to be further optimised or a multi-band and/ordiversity reception is to be enabled. Such additional conductors can beprovided for directly on the coating and in contact with it or set at adistance from it, particularly in another plane of the pane. Here thecoating will have to be generally segmented in a known way in the areaof additional antenna conductors to produce HF-transmissibility. Even ifit increases the cost of manufacture, the strip-like segmented surfaceportion can within the scope of the invention be surrounded, asrequired, with additional conductors or (virtual) ground conductors beprovided for at the edge of the pane, as is known from DE 101 46 439 C1,in order to optimise the antenna function.

The slot antenna formed from the segmented surface portion and also anyfurther antennas can be contacted in a known way either by electriccontact with the conductive boundary of the segmented surface portion orvia a capacitive or inductive coupling to this. The latter variant isespecially effective if the antenna pane is designed as a laminatedglass pane and the coating is arranged within the laminated glass. Theelectrically conductive coating will then be located either on one ofthe inner surfaces of the glass panes or on a (PET) base film. Whencontacting the slot antenna and also other antennas or any furtherelectrical elements of the antenna pane suitable measures must be takento ensure that the contact or connecting conductors do not cross theslot in such a way as to undesirably short-circuit this (see DE 101 46439 C1 and the PCT application with file reference PCT/EP02/10399).

Any heatable area provided for must be contacted in the usual wayelectrically with the aid of highly conductive bus bars consisting, forexample, of printed and baked silver frit, copper strips, if necessary,bonded on with conductive adhesive, or the like.

Further electrical elements such as passive switching elements, feedconductors, amplifiers, sensors and the like can be alternatively oradditionally incorporated on or in the antenna pane in accordance withthe invention. Here within the scope of the invention it is alsopreferred to generate the further electrical elements from theelectrically conductive coating as far as possible with the aid ofbarrier lines to enable fitting of additional conductor structures in oron the antenna pane to be extensively dispensed with.

The barrier lines required for realisation of the invention are verypreferably generated by means of laser technology. Here the coating canbe treated both on the not yet finally further-processed coated glasspane or coated film and after their being processed to a monolithic or alaminated end product such as laminated safety glass. Here YAG lasershave proved particularly effective. Local (electro)chemical processing,electroerosion or maskings are also suitable, but these are normallymore expensive and less versatile.

The electrically conductive coating will normally cover essentially thewhole of the antenna pane surface, particularly if it is used for solarcontrol purposes or as a low E-coating. Here, however, it can beprovided for that individual areas of the coating can be either blankedout by masking or the like when the coating is applied already orremoved afterwards from areas of the surface. This is to be recommendedparticularly for invisible marginal areas of the coating to preventcorrosion or undesired capacitive coupling or short-circuiting of thecoating to the metal bodywork. Such uncoated areas can, if necessary, beincorporated in a slot antenna comprising a segmented surface portion inaccordance with the invention, thus further increasing construction andstyling options.

Suitable electrically conductive coatings within the scope of theinvention will have a surface resistance which is considerably below Ω/□(ohms per square), particularly below about 10 Ω/□ and preferably below5 Ω/□. For this purpose particularly coating systems with at lease onesilver layer are suitable.

Any uncoated areas are for aesthetic reasons preferably optically maskedwith an opaque screen print or the like, which may be designedparticularly broad-surface or as a partially transparent raster. Asimilar means can be provided for to at least partly optically mask thebarrier lines and in particular the segmented surface portion used as aslot antenna, even if due to the small barrier line width this is notabsolutely necessary within the scope of the invention.

The invention is explained in the following with the aid of somedrawings. These show:

FIG. 1 a basic embodiment of the invention,

FIGS. 2-10 various embodiments of the invention.

The Figures represent non-scale schematic drawings. The structuresrepresented show projections in the plane of the drawing. In the case ofreal antenna panes individual structural elements can, as explained inthe foregoing, also be arranged in different planes of the pane. Agraphical representation of three-dimensional arrangements has beendispensed with for the sake of clarity. It goes without saying that inthe case of motor vehicle antenna panes the specific conductorstructures and barrier line arrangements must be designed and optimisedto suit the section of bodywork available. The invention is explainedwith the aid of a motor vehicle antenna pane, although this should notbe understood to mean that possible applications are limited to this. Inthe drawings identical reference numbers signify elements with identicalfunctions. Where “horizontal” and “vertical” are used in the following,they refer to the schematic graphic representation with the antenna panevertically aligned. It goes without saying that real antenna panes areusually installed in motor vehicles more or less at a considerableangle, thus enabling antennas of the antenna panes to normally receivehorizontally and vertically polarised radiation.

The antenna pane in FIG. 1, which represents a basic embodiment of theinvention, comprises at least one glass pane 1 with an edge 2, hereshown schematically as a trapezoid. The glass pane 1 can be of inorganicor organic glass. It is usually transparent. Not shown is the motorvehicle bodywork, which is at least partly of metal, entirely or partlysurrounding the glass pane 1. On the glass pane 1 or a film attached tothe glass pane 1 is an electrically conductive coating 3, which isindicated by fine dots. The electrically conductive coating 3 willusually also be transparent, enabling the glass pane 1 with the coating3 together to offer a transparency higher than the legally prescribedminimum values. Towards the edge 2 of the pane an uncoated area 11—whichwithin the scope of the invention is not absolutely essential—isprovided for to prevent HF or DC short-circuiting of the coating 3 tothe bodywork or to protect the coating 3 from corrosion.

Close to the upper edge 2 of the pane a horizontally arranged,strip-like, rectangular segmented surface portion 5 the boundaries andindividual segments of which are produced by thin barrier lines 4subsequently generated in the coating 3 by laser treatment or othermeans is provided for. As will be seen later, the segmented surfaceportion 5 need not always take the form of a slender rectangle, but cantake various forms, particularly angular, U-shaped or arched, curved,annular or polygonal annular forms, depending on the requirement and thespace available.

The width of the barrier lines 4 is made as small as possible to reduceimpairment of vision, but large enough to reliably electrically separatethe segments isolated by them. It will be typically about 0.05-0.1 mm.The barrier lines 4 inside the segmented surface portion 5 form aregular square raster over the entire surface portion 5, the size of theraster units of which is at least about one order of magnitude below thewavelength which the segmented surface portion 5 is to be able totransmit. It may even be helpful to use a raster in the area of only onehundredth of the wavelength.

Here, independently of the wavelength, in addition to the barrier lines4 forming the edge boundaries of the segmented surface portion 5 atleast one barrier line 4 must be provided for along the length of andwithin the segmented surface portion 5, since without such an interiorbarrier line 4 there is a danger of capacitive or even electricshort-circuiting across the segmented surface portion 5 which may impairits function as a slot antenna. Preferably, however, within the scope ofthe invention several interior barrier lines 4 at least extending alongthe length of the segmented surface portion 5 are always provided.

Approximately in the middle of the longer sides 6 of the segmentedsurface portion 5 and above and below this merely schematicallysuggested strip-like contact areas 7 in which a connecting cable 8 canbe connected HF-conductively to the electrically conductive coating 3 byits core 9 and its screening 10 are provided for. In the contact areas7, as required, separate conductive connection surfaces can be providedfor, particularly in the case of capacitive coupling to the coating 3.In the case of electrical coupling of the connecting cable 8 to thecoating 3, on the other hand, the core 9 and the screening 10 can alsobe connected directly to the coating 3 by e.g. soldering, frictionwelding or by means of conductive adhesive without additional conductiveconnecting surfaces in the contact areas 7.

The segmented surface portion 5 constructed as a slot antenna for VHFradiation in the example of a windscreen or rear window pane shown has alength corresponding to about half the mean wavelength of the radiationto be received, taking into consideration the dielectric shorteningfactor of the glass pane 2. For a VHF frequency of 100 MHz, for example,the wavelength is about 3 m. With a shortening factor for glass panes ofabout 0.6-0.7 the optimum length of the segmented surface portion 5 forthis frequency is thus about 1 m. Here for its function as a slotantenna deviations in the length of the segmented surface portion 5 fromoptimum λ/2 are even permitted, approximately in the range λ/4 to λ.Lengths of n*λ/2 (n=3, 5 etc.) are even possible. The width of thesegmented surface portion 5 must always be considerably less than itslength for its function as a slot antenna. While the reception bandwidthof a slot antenna increases as the width of its slot increases, itsreceptive power (signal-to-noise ratio) decreases for the meanfrequency. It has been found that for the VHF range the width of theslot antenna and thus of the segmented surface portion 5 should not beappreciably below about 1 cm.

To function as a slot antenna, a closed HF circuit must be producedaround the segmented surface portion 5 between the contact areas 7 onits longer sides 6. This may be produced particularly by surrounding thesegmented surface portion 5 on all sides, as shown, with an unsegmentedand electrically conductive area of the coating 3. The antenna functionis not impaired, however, if there are capacitive or inductive breaks inthe aforementioned HF circuit. Thus, if the segmented surface portion 5is arranged close to the edge, the metal bodywork can also beincorporated into the HF circuit by capacitive coupling to theelectrically conductive coating 3.

The core 9 of connecting cable 8 connected to the bottom longer side 6of the segmented surface portion 5 must be arranged so that noshort-circuiting of the slot antenna can occur in its connecting area.This can be achieved, for example, by running the core 9 at a sufficientdistance from the segmented surface portion 5, that is, at least about 1cm above or below the plane of the drawing (see PCT applicationPCT/EP02/10399).

The contact areas 7 need not necessarily be arranged in the longitudinalmiddle of the segmented surface portion 5. It may rather be preferable,particularly for reasons of impedance matching, to provide for thecontact areas 7 to be located off centre.

The embodiment of FIG. 2 differs from that of FIG. 1 in that, on the onehand, the uncoated area 11 close to the edge is dispensed with, and, onthe other, the segmented surface portion 5 incorporates a constriction12. This is distinguished by the fact that a slender rectangular portionof the coating 3 extending from the lower longer side 6 of the segmentedsurface portion 5 towards its upper longer side 6 has no barrier lines 4running through it and so is not segmented. The constriction 12 alsoleaves a strip of the segmented surface portion 5 at least about 1 cmwide towards the upper longer side 6 to prevent the slot antenna formedby the segmented surface portion 5 from being short-circuited in theconnecting area. The lower contact area 7 can be moved nearer the upperedge 2 of the pane by providing for the constriction 12 and thus, ifnecessary, be kept out of the vision area of the antenna pane.

The embodiment of FIG. 3 is a modification of that in accordance withFIG. 2 in that the segmented surface portion 5 incorporates areas withdifferent raster forms. In the two lower outer portions of the segmentedsurface portion 5 the barrier lines 4 are not arranged as a squareraster as in the other areas, but as a horizontal linear raster. Sincethe slot antenna formed by the segmented surface portion 5 receivesvertically (i.e. perpendicularly to the longitudinal extension of theslot antenna) polarised VHF radiation and no interfering electricshort-circuiting occurs in the areas concerned, vertical barrier lines 4can be dispensed with there.

The embodiment of FIG. 4 represents a further development of that inFIG. 3. The segmented surface portion 5 incorporates at its center wherethe contact areas 7 are arranged a part 13 with a finer raster than inthe other areas of the segmented surface portion 5. In contrast to thepreceding embodiments, the constriction 12 arranged in this part 13 isnot designed merely as a slender shape but as a divided λ/4 monopole formulti-range reception at higher frequencies, e.g. for mobile phonereception. The core 9 of the connecting cable 8 is connected in thelower contact area 7 to the constriction 12, which at the same timeforms the aforementioned antenna 14 for higher frequencies, thusenabling the signals of the slot antenna formed from the segmentedsurface portion 5 and of the antenna 14 integrated into it to betransmitted through the same connecting cable 8. The barrier lines 4 inthe part 13 are arranged as a square raster with a raster unit sizewhich is at least about one order of magnitude below the wavelength forwhich the antenna 14 is designed. In contrast to the precedingembodiments the screening 10 of the connecting cable 8 is not connecteddirectly to the coating 3 adjacent to the segmented surface portion 5but to the metal bodywork (not shown) at ground potential in immediateproximity to the upper longer side 6 of the segmented surface portion 5,an arrangement which because of the HF coupling of the coating 3 to thebodywork is essentially equivalent to direct contacting of the edge areaof the segmented surface portion 5.

FIG. 5 shows a variant of FIG. 4 where the end areas of the segmentedsurface portion 5 on both sides of the part 13 are provided with a finerraster with barrier lines 4 forming non-rectilinear boundaries andinside the segmented surface portion 5 with likewise non-rectilinearhorizontal barrier lines 4. This enables an increase in the bandwidth ofthe slot antenna. Moreover, the distance (raster unit size) between andthe thickness of the vertical barrier lines 4 increase towards theoutside. This enables further optimisation of the antenna function and areduction in manufacturing costs.

FIG. 6 shows a further development of the embodiment in accordance withFIG. 2. In addition to the segmented surface portion 5 connected as aslot antenna a heatable area 15 which has been produced in a trapezoidalform by generation of barrier lines 4 is provided for in the vision areaof the glass pane 1. Arranged on the side edges of the heatable area 15are highly conductive bus bars 16 which enable an even current supply tothe heatable area 15 and to which the—here merely suggested—heatingpanel connections 17 running to the current source (battery,accumulator, generator, etc.) are connected. Between the bus bars 16 theheatable area 15 is subdivided into horizontal segments by additionalstraight barrier lines 4 to achieve a homogenisation of the currentflow. With this, as with other variants, it is within the scope of theinvention to use the heatable area 15, as required, as a VHF/AM antennaby a circuit arrangement which is familiar to the expert and so notrepresented here.

In the case of the embodiment in FIG. 7 two segmented surface portions 5wired as slot antennas are provided for. The first segmented surfaceportion 5 extends in an arched form along the upper edge 2 and the left-and right-hand side edges 2 of the pane, while the second is arrangedclose to the lower edge 2 of the pane. Owing to the different positionand form of the two slot antennas they may be used for multi-bandreception in the VHF range and for diversity purposes. The firstsegmented surface portion 5 incorporates a square raster composed ofhorizontal and vertical barrier lines 4, while the second segmentedsurface portion 5 is divided up only horizontally by horizontal barrierlines 4. Both slot antennas are—in the case of an almost verticallyfitted antenna pane—primarily designed for the reception of verticallypolarised VHF radiation, while due to the nearly vertically arrangedside portions the slot antenna formed from the first segmented surfaceportion 5 is also able to receive horizontally polarised VHF radiation.

In the vision area again a trapezoidal heatable area 15 which isgenerated from the electrically conductive coating 3 with the aid ofadditional barrier lines 4 running all round is provided for. Incontrast to FIG. 6, the bus bars 16 in the represented embodiment arearranged horizontally, the upper bus bar 16 being extended downwards onthe left-hand side, thus enabling the heating panel connections 17 to bearranged adjacent to one another. Here, too, between the bus bars 16 theheatable area 15 is subdivided by a few essentially vertically arrangedbarrier lines 4 into segments which limit the current flow to thesegments. The represented barrier lines 4 should be regarded merely asexemplary and explanatory. Other barrier line configurations and, ifnecessary, total dispensation with segmentation of the heatable area 15are possible, depending on requirements.

FIG. 8 shows a variant of the embodiment in accordance with FIG. 7 whereinstead of the arched first segmented surface portion 5 two separateangled segmented surface portions 5 are arranged in the area of theupper left- and right-hand corner of the glass pane 1. The barrier lines4 run diagonally inside the angled segmented surface portions 5 to forma square raster. This shows that the barrier lines 4 inside thesegmented surface portion 5 do not necessarily have to run parallel withthe barrier lines 4 forming its boundaries. The slot antennas formedfrom the two identically dimensioned angled segmented surface portions 5are especially well suited to diversity reception in the same VHFfrequency range.

The lower segmented surface portion 5 wired like the two upper segmentedsurface portions 5 as a slot antenna and, as in FIG. 7, arranged in thearea of the bottom edge 2 of the pane differs from the embodiment inaccordance with FIG. 7 in that the horizontal barrier lines 4 inside thesegmented surface portion 5 are not straight but undulating, anarrangement which may be desired for optimisation of the antennafunction or for improving vision.

In the area of the connecting portion of the upper bus bar 16 arrangedon the left-hand side and particularly below its lower end more barrierlines 4 are provided for than on the embodiment in accordance with FIG.7 in order to provide even greater protection against short-circuitingin the especially critical area of the adjacent ends of the bus bars 16.

FIG. 9 shows an embodiment with three slot antennas formed fromsegmented surface portions 5 in the upper third of the pane. Two angledsegmented surface portions 5 correspond to those in FIG. 8. Provided forbelow these is a further horizontal segmented surface portion 5 which issegmented by barrier lines 4 arranged in a horizontal raster and alsoincorporates some vertical barrier lines 4 the distance between whichincreases towards the ends of the segmented surface portion 5 withoutappreciably impairing the effectiveness of the antenna by comparisonwith a version where the distance between the barrier lines 4 is evenand small, as in the center of the pane. Arranged below the three slotantennas is a heatable area 15 which has a form which deviates from thetrapezoidal and bulges upwards in the middle. The heatable area 15 iselectrically isolated from the three slot antennas at the top by acurved barrier line 4. The barrier lines 4 segmenting the heatable area15 also have a curved form the radius of which increases from the topdown to accurately influence the direction of current flow.

Finally, FIG. 10 shows a variant of FIG. 9 where an AM antenna 18 isprovided for in place of the middle slot antenna. The AM antenna 18 isformed of a strip-like, horizontal, unsegmented surface portion of theelectrically conductive coating 3 which is electrically isolated allaround from the rest of the coating 3 by barrier lines 4. The AM antenna18 is provided in the middle of its upper longer side with a flat AMantenna connecting area 19, which may be, for example, a capacitivecoupling electrode or even an electrical connection. Connected to the AMantenna area 19 is a vertical strip of the coating 3 terminated on theleft- and right-hand side by barrier lines 4 and extending as far as theedge 2 of the pane. There a connecting cable 8 by its core 9 isconnected electrically to the strip of the coating 3 in a contact area 7and thereby to the AM antenna connecting area 19. The aforementionedstrip of the coating 3 at the same time separates the two angledsegmented surface portions 5 which are, as in the preceding diagrams,wired as slot antennas.

The embodiments represented serve merely to explain the teaching of theinvention. It goes without saying that the individual elements andfeatures of the antenna panes shown may also be combined andinterchanged one with another. Solely embodiments have been shown wherethe functional structures (transmission lines, heatingconductors)—except for connecting elements and bus bars—have beengenerated from the coating 3 with the aid of barrier lines 4. To avoidimpairing the clarity of the drawings, representation of theaforementioned many diverse possibilities within the scope of theinvention to implement further functional optimisations by the use ofadditional conductors or to integrate additional functional elements inthe antenna pane have been dispensed with.

1. An antenna pane comprising at least one glass pane and at least oneelectrically conductive coating which is subdivided by barrier linesinto a number of electrically isolated segments, on the antenna pane thecoating incorporates at least one strip-like segmented surface portionin which the distance between the barrier lines is so small that thecoating there can transmit HF radiation in a specified frequency range,wherein the segmented surface portion is, by contact with a feed lineand a ground line in contact areas at its two longitudinal sides and byits outer dimensions, constructed as a slot antenna for electromagneticradiation in the range of frequencies which the segmented surfaceportion can transmit.
 2. The antenna pane in accordance with claim 1,wherein the barrier lines within the segmented surface portion form alinear or lattice raster with a constant raster unit size.
 3. Theantenna pane in accordance with claim 1, wherein the barrier lineswithin the segmented surface portion form a raster with a variableraster unit size, variable barrier line width or variable raster form.4. The antenna pane in accordance with claim 1, wherein the barrierlines within the segmented surface portion have at least partly anon-rectilinear form.
 5. The antenna pane in accordance with claim 1,wherein the segmented surface portion is constructed as a slot antennafor VHF range.
 6. The antenna pane in accordance with claim 5, whereinin a part of the segmented surface portion a raster which can transmitfrequencies above the VHF range and is finer than in other areas of thesegmented surface portion is provided and in that at least one antennafor frequencies above the VHF range is arranged in this part.
 7. Theantenna pane in accordance with claim 1, wherein the segmented surfaceportion in an area in which it is contacted as a slot antennaincorporates a constriction which reduces a width of the segmentedsurface portion.
 8. The antenna pane in accordance with claim 7, whereinthe constriction comprises a strip-like portion of the coating, thestrip-like portion projects into the segmented surface portion and isconstructed as an antenna for a frequency range above a reception rangeof the slot antenna.
 9. The antenna pane in accordance with claim 1,wherein the barrier lines are first barrier lines, and wherein thecoating incorporates a heatable area electrically isolated from an areaof the coating adjacent to the segmented surface portion by at least onesecond barrier line and provided with bus bars.
 10. The antenna pane inaccordance with claim 9, wherein the heatable area is provided with atleast some of the second barrier lines influencing distribution ofheating current.
 11. The antenna pane in accordance with claim 9,wherein the heatable area is wired as an antenna for VHF and/or AMrange.
 12. The antenna pane in accordance with claim 1, wherein in thecoating an AM antenna bounded by at least some of the barrier lines andwith an assigned AM antenna connecting area is provided.
 13. The antennapane in accordance with claim 1, wherein the segmented surface portionis surrounded on all sides by the electrically conductive coating. 14.The antenna pane in accordance with claim 4, wherein the non-rectilinearform is one of an undulating, curved, zigzagged and fractal form. 15.The antenna pane in accordance with claim 2, wherein the barrier lineswithin the segmented surface portion have at least partly anon-rectilinear form.
 16. The antenna pane in accordance with claim 2,wherein the segmented surface portion is constructed as a slot antennafor VHF range.
 17. The antenna pane in accordance with claim 2, whereinthe segmented surface portion in an area in which it is contacted as aslot antenna incorporates a constriction which reduces a width of thesegmented surface portion.
 18. The antenna pane in accordance with claim2, wherein the coating incorporates a heatable area electricallyisolated from an area of the coating adjacent to the segmented surfaceportion by at least one of the barrier lines and provided with bus bars.19. The antenna pane in accordance with claim 2, including an AM antennaprovided in the coating and bounded by the barrier lines, the AM antennacomprising an assigned AM antenna connecting area.
 20. The antenna panein accordance with claim 2, wherein the segmented surface portion issurrounded on all sides by the electrically conductive coating.